Another week, and another Greek crisis looms. It might seem only yesterday that the markets were on tenterhooks over whether the country would finally bring its miserable experiment in sharing a currency with Germany and France to an end, or whether there would be a last-minute compromise that would keep the show on the road for a few more months. Now, with elections due on September 20, and no clear victor likely, the whole circus is about to start up again...

There is, however, an election coming up that genuinely matters to the future of the single currency -- only it is taking place not in Greece, but in Poland. When that country elects a new government next month, the likely victor, the Law & Justice Party, will effectively close off the option of joining the euro one day. In reality, Greece was always too small and chaotic an economy to matter one way or another to the eurozone. But if Poland, along with the other rising economic powers of eastern Europe, turns its back on the euro, then that is far more serious.